"I believe that the current limits on press freedom and excessive government secrecy make it impossible for Americans to grasp fully what is happening in the wars we finance."

She said that during the 2010 elections in Iraq, the media duped the world into thinking that all was well.

"You might remember that the American press was flooded with stories declaring the elections a success, complete with upbeat anecdotes and photographs of Iraqi women proudly displaying their ink-stained fingers," she wrote. "The subtext was that United States military operations had succeeded in creating a stable and democratic Iraq. Those of us stationed there were acutely aware of a more complicated reality."

She said at the time, she got regular reports detailing security forces' crackdown against dissidents "on behalf" of Prime Minister Nuri al-Maliki.

"I was shocked by our military's complicity in the corruption of that election," she said. "Yet these deeply troubling details flew under the American media's radar."

Sunni militant fighters are vowing to capture cities in Iraq and threatening the government of al-Maliki. Some Iraqi security forces, most of whom were trained by the United States, have bolted their posts in areas overrun by militants.

U.S. President Barack Obama has said he will not send troops to Iraq, but is considering other options.

"This is not going to happen overnight," the President said Friday. He added that unless Iraq fixes its internal political problems, short-term military help from the United States won't make much difference.

Pressure for the United States to provide military support to Iraq's struggling government has increased, with conservative Republicans blaming Obama for creating a security vacuum in 2011 by pulling out U.S. troops.

GOP critics also say that Obama's unwillingness to provide significant military backing to opposition forces in Syria's civil war has made it easier for the militant Islamic State in Iraq and Syria, or ISIS, to attack in Iraq.

Obama, however, has resisted getting drawn into another military engagement there after the ending the nine-year conflict started by his predecessor.

Manning also slammed the practice of embedding journalists with the military.

"Reporters naturally fear having their access terminated, so they tend to avoid controversial reporting that could raise red flags," Manning wrote.

Bradley Manning and Edward Snowden both held jobs that gave them access to some of their country's most secret and sensitive intelligence. They chose to share that material with the world and are now paying for it.